IP address allocation method, and device

ABSTRACT

An Internet Protocol (IP) address allocation method and a device to resolve a technical problem that an IP address conflict occurs when a control plane device and a user plane device allocate an IP address for one user equipment (UE) at the same time. When receiving a session establishment request message, a control plane network device may determine whether a first user plane network device is capable of allocating an IP address for a terminal device. If the first user plane network device is capable of allocating the IP address for the terminal device, the control plane network device may send an address allocation indication to the first user plane network device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/039,225, filed on Jul. 18, 2018, which is a continuation ofInternational Patent Application No. PCT/CN2016/071393, filed on Jan.19, 2016. All of the aforementioned patent applications are herebyincorporated by reference in their entireties.

TECHNICAL FIELD

The present disclosure relates to the field of mobile communicationstechnologies, and in particular, to an Internet Protocol (IP) addressallocation method and a device.

BACKGROUND

In other approaches, when a user equipment (UE) is in a process ofattaching to a network or in a procedure of establishing a packet datanetwork (PDN) connection requested by the UE, a network deviceestablishes a default bearer for the UE. At the same time, the networkdevice allocates a corresponding IP address to the UE. Currently, a PDNgateway (P-GW) usually allocates the IP address for the UE.

With evolution of a network architecture towards a 4.5th generation(4.5G) mobile communications system/5th generation (5G) mobilecommunications system, separation of a control plane and a user plane ofa network function is a main trend. If the P-GW is separated into acontrol plane device and a user plane device, an IP address allocationfunction of the P-GW may be inherited by the control plane device or maybe inherited by the user plane device, in other words, both the controlplane device and the user plane device may be capable of allocating theIP address. In this case, if the control plane device and the user planedevice allocate an IP address for one UE at the same time, a problem ofan IP address conflict is caused. Currently, there is still no solutionfor this problem.

SUMMARY

This application provides an IP address allocation method and a device,in order to resolve a technical problem that an IP address conflictoccurs when a control plane device and a user plane device allocate anIP address for one UE at the same time.

According to a first aspect, a first IP address allocation method isprovided, including: receiving, by a control plane network device, asession establishment request message, where the session establishmentrequest message is used to establish a session connection for a requestof a terminal device; determining, by the control plane network devicebased on service information that is requested by the terminal deviceand that is carried in the session establishment request message andbased on service capability information of a first user plane networkdevice, whether the first user plane network device is capable ofallocating an IP address for the terminal device; and if the first userplane network device is capable of allocating the IP address for theterminal device, sending, by the control plane network device, anaddress allocation indication to the first user plane network device.

When receiving the session establishment request message, the controlplane network device may determine whether the first user plane networkdevice is capable of allocating the IP address for the terminal device.If the first user plane network device is capable of allocating the IPaddress for the terminal device, the control plane network device maysend the address allocation indication to the first user plane networkdevice. In this way, which device allocates the IP address may bedetermined, and a case in which two devices allocate an IP address forone terminal device at the same time is avoided, thereby avoiding an IPaddress conflict.

With reference to the first aspect, in a first possible implementationof the first aspect, the determining whether the first user planenetwork device is capable of allocating an IP address for the terminaldevice includes: determining, by the control plane network device basedon the service information, a service requested by the terminal device;and determining, by the control plane network device based on theservice capability information, whether the first user plane networkdevice is capable of allocating an IP address for the service requestedby the terminal device.

A manner of determining whether the first user plane network device iscapable of allocating the IP address for the terminal device isprovided.

With reference to the first aspect or the first possible implementationof the first aspect, in a second possible implementation of the firstaspect, the method further includes: receiving, by the control planenetwork device, the service capability information of the first userplane network device sent by the first user plane network device; orobtaining, by the control plane network device, pre-configure servicecapability information of the first user plane network device.

The control plane network device may obtain the service capabilityinformation of the first user plane network device in different manners,and this is relatively flexible.

With reference to the first aspect or the first possible implementationor the second possible implementation of the first aspect, in a thirdpossible implementation of the first aspect, the address allocationindication includes address allocation manner information, and theaddress allocation manner information is used to indicate a manner inwhich the first user plane network device is to allocate the IP addressfor the terminal device.

The address allocation indication may further carry the addressallocation manner information, such that the first user plane networkdevice can determine which manner should be used to allocate the IPaddress for the terminal device, in order to effectively reduce aprobability of an allocation error.

With reference to the third possible implementation of the first aspect,in a fourth possible implementation of the first aspect, the controlplane network device obtains, by resolving the session establishmentrequest message, the address allocation manner information carried inthe session establishment request message.

To be more specific, the control plane network device may obtain theaddress allocation manner information using the session establishmentrequest message sent by the terminal device, and the address allocationmanner information obtained in such a manner is more representative ofan intention of the terminal device.

With reference to any one of the first aspect, or the first possibleimplementation to the fourth possible implementation of the firstaspect, in a fifth possible implementation of the first aspect, theaddress allocation indication further includes the service informationrequested by the terminal device.

The address allocation indication may further include the serviceinformation requested by the terminal device, such that the first userplane network device allocates the IP address for the terminal device.

With reference to any one of the first aspect, or the first possibleimplementation to the fifth possible implementation of the first aspect,in a sixth possible implementation of the first aspect, the addressallocation indication further includes indication information, and theindication information is used to instruct the first user plane networkdevice to allocate the IP address for the terminal device.

The address allocation indication may explicitly instruct the first userplane network device to allocate the IP address for the terminal device.In this way, the first user plane network device can quickly determine atask to be performed by the first user plane network device, and anindication manner is relatively clear and easy to understand.

According to a second aspect, a second IP address allocation method isprovided, including: receiving, by a user plane network device, anaddress allocation indication of a control plane network device;determining, by the user plane network device based on addressallocation manner information included in the address allocationindication, a manner of allocating an IP address for the terminaldevice; and allocating, by the user plane network device, the IP addressfor the terminal device based on the determined manner.

The control plane network device may send the address allocationindication to a first user plane network device, in order to indicate amanner in which the first user plane network device is to allocate theIP address for the terminal device. In this way, which device allocatesthe IP address may be determined, avoiding a case in which two devicesallocate an IP address for one terminal device at the same time, therebyavoiding an IP address conflict. In addition, a manner of allocating theIP address for the terminal device by the first user plane networkdevice may be explicitly indicated, in order to help the first userplane network device perform an operation.

With reference to the second aspect, in a first possible implementationof the second aspect, the method further includes sending, by the userplane network device, service capability information of the user planenetwork device to the control plane network device.

The user plane network device may send the service capabilityinformation of the user plane network device to the control planenetwork device, such that the control plane network device determineswhether the user plane network device can allocate the IP address forthe corresponding terminal device.

With reference to the second aspect or the first possible implementationof the second aspect, in a second possible implementation of the secondaspect, the address allocation indication further includes indicationinformation, and the indication information is used to instruct the userplane network device to allocate the IP address for the terminal device.

The control plane network device may instruct, in an explicit indicationmanner, the user plane network device to allocate the IP address for theterminal device. As such, the user plane network device can gain atimely understanding.

With reference to the second aspect or the first possible implementationor the second possible implementation of the second aspect, in a thirdpossible implementation of the second aspect, if the manner ofallocating the IP address for the terminal device is allocating the IPaddress by the user plane network device in a process of establishing adefault bearer, and the address allocation indication further includesservice information, the allocating, by the user plane network device,the IP address for the terminal device based on the determined mannerincludes: allocating, by the user plane network device, the IP addressfor the terminal device based on the service information; and sending,by the user plane network device, a session response message to thecontrol plane network device, where the session response message carriesthe IP address.

If the address allocation manner information is used to instruct theuser plane network device to allocate the IP address in the process ofestablishing the default bearer, the user plane network device maycarry, in the session response message, the IP address allocated to theterminal device. The user plane network device can determine, using theaddress allocation manner information, when to allocate the IP addressfor the terminal device.

With reference to the second aspect or the first possible implementationor the second possible implementation of the second aspect, in a fourthpossible implementation of the second aspect, if the manner ofallocating the IP address for the terminal device is allocating the IPaddress by the user plane network device after a default bearer isestablished, the allocating, by the user plane network device, the IPaddress for the terminal device based on the determined manner includes:receiving, by the user plane network device, a request message that issent by the terminal device using a user plane connection, where therequest message carries service information requested by the terminaldevice; allocating, by the user plane network device, the IP address forthe terminal device based on the service information; and sending, bythe user plane network device, the IP address for the terminal deviceusing the user plane connection.

If the address allocation manner information is used to instruct theuser plane network device to allocate the IP address in the process ofestablishing the default bearer, the user plane network device mayallocate the IP address for the terminal device after receiving therequest message sent by the terminal device. The user plane networkdevice can determine, using the address allocation manner information,when to allocate the IP address for the terminal device.

With reference to the third possible implementation or the fourthpossible implementation of the second aspect, in a fifth possibleimplementation of the second aspect, the allocating, by the user planenetwork device, the IP address for the terminal device based on theservice information includes: determining, by the user plane networkdevice using the service information, a server that allocates the IPaddress for the terminal device; sending, by the user plane networkdevice, an address allocation request message to the server, where theaddress allocation request message is used to request to allocate the IPaddress for the terminal device; and receiving, by the user planenetwork device, the IP address that is allocated to the terminal deviceand that is sent by the server.

The user plane network device may determine, using the serviceinformation carried in the request message, the server that allocatesthe IP address for the terminal device, and then request the server toallocate the IP address for the terminal device, such that accuracy isrelatively high.

With reference to the fifth possible implementation of the secondaspect, in a sixth possible implementation of the second aspect, thedetermining, by the user plane network device using the serviceinformation, a server that allocates the IP address for the terminaldevice includes: determining, by the user plane network device using theservice information, that the server that allocates the IP address forthe terminal device is a Dynamic Host Configuration Protocol (DHCP)server. Additionally, the sending, by the user plane network device, anaddress allocation request message to the server includes: sending, bythe user plane network device, the address allocation request message tothe DHCP server based on a configured address of the DHCP server.

With reference to the fifth possible implementation of the secondaspect, in a seventh possible implementation of the second aspect, thedetermining, by the user plane network device using the serviceinformation, a server that allocates the IP address for the terminaldevice includes: determining, by the user plane network device using theservice information, that the server that allocates the IP address forthe terminal is a Layer 2 Tunneling Protocol (L2TP) network server(LNS). Additionally, the sending, by the user plane network device, anaddress allocation request message to the server includes: establishing,by the user plane network device, an L2TP link to the LNS based on aconfigured address of the LNS; and sending, by the user plane networkdevice, the address allocation request message to the LNS using the L2TPlink.

With reference to the fifth possible implementation of the secondaspect, in an eighth possible implementation of the second aspect, thedetermining, by the user plane network device using the serviceinformation, a server that allocates the IP address for the terminaldevice includes: determining, by the user plane network device using theservice information, that the server that allocates the IP address forthe terminal device is an Authentication, Authorization and Accounting(AAA) server. Additionally, the sending, by the user plane networkdevice, an address allocation request message to the server includes:sending, by the user plane network device, the address allocationrequest message to the AAA server based on a configured address of theAAA server.

The foregoing provides several manners in which the user plane networkdevice allocates the IP address for the terminal device using anexternal server. The user plane network device may request more externalservers and have more abundant resources. In addition, the user planenetwork device may initiate a request to different servers based on theservice information, such that an allocation result better meets arequirement of the terminal device.

According to a third aspect, a control plane network device is provided,including: a receiver configured to receive a session establishmentrequest message, where the session establishment request message is usedto establish a session connection for a request of a terminal device;and a processor configured to: determine, based on service informationthat is requested by the terminal device and that is carried in thesession establishment request message and based on service capabilityinformation that a first user plane network device is able to provide,whether the first user plane network device is capable of allocating anIP address for the terminal device, and if the first user plane networkdevice is capable of allocating the IP address for the terminal device,send an address allocation indication to the first user plane networkdevice.

With reference to the third aspect, in a first possible implementationof the third aspect, the processor is configured to: determine, based onthe service information, a service requested by the terminal device; anddetermine, based on the service capability information, whether thefirst user plane network device is capable of allocating an IP addressfor the service requested by the terminal device.

With reference to the third aspect or the first possible implementationof the third aspect, in a second possible implementation of the thirdaspect, the receiver is further configured to receive the servicecapability information of the first user plane network device sent bythe first user plane network device. Alternatively, the processor isfurther configured to obtain pre-configure service capabilityinformation of the first user plane network device.

With reference to the third aspect or the first possible implementationor the second possible implementation of the third aspect, in a thirdpossible implementation of the third aspect, the address allocationindication includes address allocation manner information, and theaddress allocation manner information is used to indicate a manner inwhich the first user plane network device is to allocate the IP addressfor the terminal device.

With reference to the third possible implementation of the third aspect,in a fourth possible implementation of the third aspect, the processoris further configured to: obtain, by resolving the session establishmentrequest message, the address allocation manner information carried inthe session establishment request message.

With reference to any one of the third aspect, or the first possibleimplementation to the fourth possible implementation of the thirdaspect, in a fifth possible implementation of the third aspect, theaddress allocation indication further includes the service informationrequested by the terminal device.

With reference to any one of the third aspect, or the first possibleimplementation to the fifth possible implementation of the third aspect,in a sixth possible implementation of the third aspect, the addressallocation indication further includes indication information, and theindication information is used to instruct the first user plane networkdevice to allocate the IP address for the terminal device.

According to a fourth aspect, a user plane network device is provided,including a first receiver configured to receive an address allocationindication of a control plane network device. The user plane networkdevice further includes a processor configured to: determine, based onaddress allocation manner information included in the address allocationindication, a manner of allocating an IP address for the terminaldevice; and allocate the IP address for the terminal device based on thedetermined manner.

With reference to the fourth aspect, in a first possible implementationof the fourth aspect, the user plane network device further includes afirst transmitter. The first transmitter is configured to send servicecapability information of the user plane network device to the controlplane network device.

With reference to the fourth aspect or the first possible implementationof the fourth aspect, in a second possible implementation of the fourthaspect, the address allocation indication further includes indicationinformation, and the indication information is used to instruct thefirst user plane network device to allocate the IP address for theterminal device.

With reference to the fourth aspect or the first possible implementationor the second possible implementation of the fourth aspect, in a thirdpossible implementation of the fourth aspect, if the manner ofallocating the IP address for the terminal device is allocating the IPaddress by the user plane network device in a process of establishing adefault bearer, and the address allocation indication further includesservice information, the processor is configured to: allocate the IPaddress for the terminal device based on the service information; andsend a session response message to the control plane network deviceusing the first transmitter, where the message carries the IP address.

With reference to the fourth aspect, or the first possibleimplementation or the second possible implementation of the fourthaspect, in a fourth possible implementation of the fourth aspect, theuser plane network device further includes a second receiver and asecond transmitter; and if the manner of allocating the IP address forthe terminal device is allocating the IP address by the user planenetwork device after a default bearer is established, the processor isconfigured to: receive, using the second receiver, a request messagethat is sent by the terminal device using a user plane connection, wherethe request message carries service information requested by theterminal device; allocate the IP address for the terminal device basedon the service information; and send the IP address for the terminaldevice using the second transmitter and the user plane connection.

With reference to the third possible implementation or the fourthpossible implementation of the fourth aspect, in a fifth possibleimplementation of the fourth aspect, the user plane network devicefurther includes a third receiver and a third transmitter, and theprocessor is configured to: determine, using the service information, aserver that allocates the IP address for the terminal device; send anaddress allocation request message to the server using the thirdtransmitter, where the address allocation request message is used torequest to allocate the IP address for the terminal device; and receive,using the third receiver, the IP address that is allocated to theterminal device and that is sent by the server.

With reference to the fifth possible implementation of the fourthaspect, in a sixth possible implementation of the fourth aspect, theprocessor is configured to: determine, using the service information,that the server that allocates the IP address for the terminal device isa DHCP server; and send the address allocation request message to theDHCP server using the third transmitter based on a configured address ofthe DHCP server.

With reference to the fifth possible implementation of the fourthaspect, in a seventh possible implementation of the fourth aspect, theprocessor is configured to: determine, using the service information,that the server that allocates the IP address for the terminal is anLNS; establish an L2TP link to the LNS based on a configured address ofthe LNS; and send the address allocation request message to the LNSusing the third transmitter and the L2TP link.

With reference to the fifth possible implementation of the fourthaspect, in an eighth possible implementation of the fourth aspect, theprocessor is configured to: determine, using the service information,that the server that allocates the IP address for the terminal device isan AAA server; and send the address allocation request message to theAAA server using the third transmitter based on a configured address ofthe AAA server.

According to a fifth aspect, a network system is provided, including thecontrol plane network device in the fourth aspect and the user planenetwork device in the fifth aspect.

According to a sixth aspect, another control plane network device isprovided, including a module configured to implement the method in thefirst aspect.

According to a seventh aspect, another user plane network device isprovided, including a module configured to implement the method in thesecond aspect.

According to an eighth aspect, another network system is provided,including the control plane network device in the sixth aspect and theuser plane network device in the seventh aspect.

When receiving the session establishment request message, the controlplane network device may determine whether the first user plane networkdevice is capable of allocating the IP address for the terminal device.If the first user plane network device is capable of allocating the IPaddress for the terminal device, the control plane network device maysend the address allocation indication to the first user plane networkdevice. In this way, which device allocates the IP address may bedetermined, and a case in which two devices allocate an IP address forone terminal device at the same time is avoided, thereby avoiding an IPaddress conflict.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in the embodiments of the presentdisclosure more clearly, the following briefly describes theaccompanying drawings required for describing the embodiments of thepresent disclosure. The accompanying drawings in the followingdescription show merely some embodiments of the present disclosure, anda person of ordinary skill in the art may still derive other drawingsfrom these accompanying drawings without creative efforts.

FIG. 1 is a first network architectural diagram in which a user planeand a control plane are separated in an Evolved Packet System (EPS)according to an embodiment of the present disclosure;

FIG. 2 is a second network architectural diagram in which a user planeand a control plane are separated in an EPS system according to anembodiment of the present disclosure;

FIG. 3 is a flowchart of a first IP address allocation method accordingto an embodiment of the present disclosure;

FIG. 4 is a flowchart of a second IP address allocation method accordingto an embodiment of the present disclosure;

FIG. 5 is a first flowchart of allocating an IP address by a DGWaccording to an embodiment of the present disclosure;

FIG. 6 is a second flowchart of allocating an IP address by a DGWaccording to an embodiment of the present disclosure;

FIG. 7A and FIG. 7B are schematic structural diagrams of a control planenetwork device according to an embodiment of the present disclosure;

FIG. 8A to FIG. 8D are schematic structural diagrams of a user planenetwork device according to an embodiment of the present disclosure;

FIG. 9 is a structural block diagram of a control plane network deviceaccording to an embodiment of the present disclosure; and

FIG. 10 is a structural block diagram of a user plane network deviceaccording to an embodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

To make the objectives, technical solutions, and advantages of theembodiments of the present disclosure clearer, the following clearlydescribes the technical solutions in the embodiments of the presentdisclosure with reference to the accompanying drawings in theembodiments of the present disclosure. The described embodiments aresome but not all of the embodiments of the present disclosure. All otherembodiments obtained by a person of ordinary skill in the art based onthe embodiments of the present disclosure without creative efforts shallfall within the protection scope of the embodiments of the presentdisclosure.

Technologies described in this specification may be applied to variouscommunications systems, for example, a Long-Term Evolution (LTE) system,a 4.5G system, or a 5G system, and other communications systems orfuture evolution systems. The technical solutions provided in thisspecification are not only applicable to a 3rd Generation PartnershipProject (3GPP) access manner, but also applicable to a case ofseparating a control plane from a user plane in a non-3GPP accessmanner.

In the following, some terms in the embodiments of the presentdisclosure are described, in order to help a person skilled in the arthave a better understanding.

(1) A terminal device is a device that provides a user with voice and/ordata connectivity, for example, may be a handheld device with a wirelessconnection function, or a processing device connected to a wirelessmodem. The terminal device may communicate with a core network using aradio access network (RAN), and exchange voice and/or data with the RAN.The terminal device may include a UE, a wireless terminal device, amobile terminal device, a subscriber unit, a subscriber station, amobile station, a remote station, an access point (AP), a remoteterminal device, an access terminal device (Access Terminal), a userterminal device (User Terminal), a user agent, or a user device. Forexample, the terminal device may include a mobile phone (or referred toas a “cellular” phone), a computer having a mobile terminal device, adedicated terminal device in a Narrowband Internet-of-Things (NB-IoT),or a portable, pocket-sized, handheld, computer built-in, or in-vehiclemobile apparatus. For example, the terminal device may include a devicesuch as a personal communications service (PCS) phone, a cordlesstelephone set, a Session Initiation Protocol (SIP) phone, a wirelesslocal loop (WLL) station, or a personal digital assistant (PDA).

(2) A network device may include, for example, a control plane networkdevice and a user plane network device.

In a network architecture of separating the control plane from the userplane (or referred to as a forwarding plane), for example, in a networkarchitecture, the control plane network device may include, for example,a control plane gateway (CGW), or in a future communications system(such as a 5G system), a current mobility management entity (MIME) andthe CGW (or including another device) may be combined to form a newcontrol plane network device, or may include another possible networkdevice configured to implement a control plane function. Alternatively,for example, in another network architecture, the control plane networkdevice may include, for example, a control plane network element of aP-GW, for example, the network element is referred to as a control planeP-GW (PGW-C), or may include another possible network device configuredto implement the control plane function.

In the network architecture of separating the control plane from theuser plane, for example, in a network architecture, the user planenetwork device may include, for example, a user plane gateway or a userplane gateway deployed closer to users (or in a distributed manner),referred to as a distributed gateway (DGW), or may include anotherpossible network device configured to implement a user plane function.Alternatively, for example, in another network architecture, the userplane network device may include, for example, a user plane networkfunction element of the P-GW, for example, the network element isreferred to as a user plane P-GW (PGW-U), or may include anotherpossible network device configured to implement the user plane function.

(3) The terms “system” and “network” may be used interchangeably in theembodiments of the present disclosure. “A plurality of” means two ormore than two. The term “and/or” describes an association relationshipfor describing associated objects and represents that threerelationships may exist. For example, A and/or B may represent thefollowing three cases: Only A exists, both A and B exist, and only Bexists. In addition, the character “/” generally indicates an “or”relationship between the associated objects unless specified otherwise.

The network architecture applied in the embodiments of the presentdisclosure is an architecture of separating the control plane from theuser plane, and the following gives a description with reference to theaccompanying drawings.

In the embodiments of the present disclosure, when the terminal devicemay access a public mobile network or a dedicated network of a specificapplication (such as an Internet service provider (ISP) or an enterprisenetwork), the embodiments of the present disclosure are mainly intendedto resolve a problem of allocating an IP address for the terminal devicein this scenario.

The following describes the network architecture in the embodiments ofthe present disclosure. When the network architecture is described, anevolved packet system (EPS) is used as an example. However, theembodiments of the present disclosure are not limited to this system.

A DGW architecture is an enhanced network architecture that is proposedon top of an existing EPS network architecture based on an idea ofseparating the control plane function of the network from the user planefunction of the network. The DGW architecture includes the CGW and theuser plane gateway (UGW).

The CGW is a centralized control plane gateway and may be implemented intwo forms: (1) integrating network elements of the control planefunctions of a serving gateway (S-GW) and a packet data network gateway(P-GW) in an existing 3GPP-defined EPS network, as shown in FIG. 1; (2)including two separate network elements for respectively implementing acontrol plane function of the existing S-GW (Control Plane S-GW) and acontrol plane function of the existing P-GW (Control Plane P-GW), forexample, a network element for implementing the control plane functionof the existing S-GW is referred to as a control plane S-GW, and anetwork element for implementing the control plane function of theexisting P-GW is referred to as the control plane P-GW, as shown in FIG.2.

The CGW may be specially configured to process control plane signalingin the EPS network, and may implement functions such as mobilitymanagement, session management, address management, path management, andcharging management. The CGW interacts with the UGW to control andmanage user plane data processing.

The PGW-C is a control plane functional entity of the P-GW and inheritsthe control plane function of the P-GW, such as a charging policy andcharging control.

The UGW is a distributed user plane gateway and corresponds to twoimplementation forms of the CGW. The UGW is also implemented in twoforms: (1) integrating network elements of user plane functions of theS-GW and P-GW in the existing EPS network, as shown in FIG. 1; (2)including two separate network elements for respectively implementing auser plane function of the existing S-GW (User Plane S-GW) and a userplane function of the existing P-GW (User Plane P-GW), for example, anetwork element for implementing the user plane function of the existingS-GW is referred to as a user plane S-GW, and a network element forimplementing the user plane function of the existing P-GW is referred toas the user plane P-GW, as shown in FIG. 2.

The UGW is specially configured to process user plane data in the EPSnetwork, and may implement functions such as routing and forwarding,packet inspection, packet statistics, and quality of service execution.The UGW processes the user plane data under control and management ofthe CGW. In addition, the UGW may also be referred to as the DGWconsidering a feature that the UGW may be deployed in a distributedmanner.

The PGW-U is a user functional entity of the P-GW and inherits the userplane function of the P-GW, such as charging information statistics.

FIG. 1 is a network architectural diagram when a CGW and a UGW areimplemented in respective first forms. In FIG. 1, a UE is connected toan evolved universal terrestrial radio access network (E-UTRAN) using aUu interface, and the E-UTRAN is connected to a DGW using an S1-Uinterface. The CGW is connected to the DGW using an Sx interface, andthe DGW is connected to a Global System for Mobile Communications(GSM)/Enhanced Data Rates for GSM Evolution Radio Access Network (GERAN)and a Universal Mobile Telecommunications Service (UMTS) terrestrialradio access network (UTRAN) using an S12 interface. The E-UTRAN isconnected to an MME using an S1-MME interface, and the MME is connectedto the CGW using an S11 interface. The MME is connected to a servinggeneral packet radio service support node (SGSN) using an S3 interface,and the MME is connected to a home subscriber server (HSS) using an S6ainterface. The CGW is connected to a policy and charging rules function(PCRF) unit using a Gx interface, and the PCRF is connected to anapplication server or a packet data network using an Rx interface (theapplication server is used as an example in FIG. 1), for example, theapplication server may include an IP multimedia subsystem (IMS) or apacket switching service (PSS).

The interface between the CGW and the DGW, interfaces between the CGWand other devices, and interfaces between the DGW and other devices aremerely an example in FIG. 1, and other interfaces may also be used.

In the architecture of FIG. 1, a signaling stream of a control plane isshown by a solid line arrow, and a signaling stream of a user plane isshown by a dashed line arrow.

FIG. 2 is a network architectural diagram when a CGW and a UGW areimplemented in respective second forms. In FIG. 2, a UE is connected toan E-UTRAN using a Uu interface, and the E-UTRAN is connected to anSGW-U using an S1-U interface. The SGW-U is connected to the SGW-C usingan Sxa interface, and the SGW-U is connected to a GERAN and a UTRANusing an S12 interface. The E-UTRAN is connected to an MME using anS1-MME interface, and the MME is connected to an SGW-C using an S11interface. The SGW-C is connected to a PGW-C using an S5-C interface.The PGW-C is connected to a PCRF using a Gx interface, and the PGW-C isconnected to the PGW-U using an Sxb interface. The PCRF is connected toan application server or a packet data network using an Rx interface(the application server is used as an example in FIG. 2), and the PGW-Uis connected to the application server or the packet data network usingan SGi interface (the application server is used as an example in FIG.2), for example, the application server may include an IMS or a PSS.

Interfaces between devices such as the SGW-C, the SGW-U, the PGW-C, andthe PGW-C, and interfaces between these devices and other devices aremerely an example in FIG. 2, and other interfaces may also be used.

In the architecture of FIG. 2, a signaling stream of a control plane isshown by a solid line arrow, and a signaling stream of a user plane isshown by a dotted line arrow.

The solutions provided in the embodiments of the present disclosure aredescribed below with reference to the accompanying drawings.

Referring to FIG. 3, a first IP address allocation method is provided,and a procedure of the method is described as follows.

Step 301. A control plane network device receives a sessionestablishment request message, where the session establishment requestmessage is used to establish a session connection for a request of aterminal device.

Step 302. The control plane network device determines, based on serviceinformation that is requested by the terminal device and that is carriedin the session establishment request message and based on servicecapability information that a first user plane network device is able toprovide, whether the first user plane network device is capable ofallocating an IP address for the terminal device.

Step 303. If the first user plane network device is capable ofallocating the IP address for the terminal device, the control planenetwork device sends an address allocation indication to the first userplane network device.

If the control plane network device determines that the first user planenetwork device is incapable of allocating the IP address for theterminal device, the control plane network device may not instruct thefirst user plane network device to allocate the IP address for theterminal device. In this case, for example, the control plane networkdevice may voluntarily allocate the IP address for the terminal device.

Referring to FIG. 4, a second IP address allocation method is provided,and a procedure of the method is described as follows.

Step 401. A user plane network device receives an address allocationindication of a control plane network device.

Step 402. The user plane network device determines, based on addressallocation manner information included in the address allocationindication, a manner of allocating an IP address for a terminal device.

Step 403. The user plane network device allocates the IP address for theterminal device based on the determined manner.

FIG. 3 and FIG. 4 show corresponding methods, which are describedtogether below. For example, FIG. 3 and FIG. 4 may be implemented basedon the architecture in FIG. 1, or FIG. 3 and FIG. 4 may be implementedbased on the architecture in FIG. 2. The following uses an example inwhich FIG. 3 and FIG. 4 are implemented based on the architecture inFIG. 1 for description. Similarly, if FIG. 3 and FIG. 4 are implementedbased on the architecture in FIG. 2, a PGW-C and a PGW-U are used torespectively replace a CGW and a DGW in FIG. 5. In addition, step 1 inFIG. 5 is replaced with a step in which an SGW-C sends a sessionestablishment request to the PGW-C, and other steps are similar.Therefore, details are not described herein again.

Optionally, the CGW needs to know service capability information thatthe DGW is able to provide. The service capability information that theDGW is able to provide may include a particular service to which the DGWis capable of allocating an IP address, for example, the terminal devicerequests a service type 1. If the DGW is capable of allocating an IPaddress for the service type 1, the DGW may allocate the IP address forthe service type 1. The CGW may obtain the service capabilityinformation of the DGW in different manners. The following describesseveral possible manners.

In a first manner, the DGW sends, to the CGW, the service capabilityinformation indicating that the DGW is capable of allocating the IPaddress.

Optionally, when the DGW is powered on and starts, the DGW generallyinitiates an Sx interface (an Sx interface is an interface used betweenthe CGW and the DGW) startup procedure. For example, the DGW sends an Sxsetup request message to the CGW. Then, the DGW may add the servicecapability information to the Sx setup request message, for example, mayadd a field to the Sx setup request message to indicate the servicecapability information of the DGW. For example, the field may be an IPallocation capability.

After receiving the Sx setup request message that carries the IPallocation capability, the CGW may save a DGW identifier carried in theSx setup request message and the IP allocation capability carried in theSx setup request message, and may return an Sx setup response message tothe DGW. In this way, the CGW knows the service capability informationof the DGW.

Alternatively, optionally, the DGW may also send the service capabilityinformation to the CGW using an event report message. For example, afterthe Sx interface starts, when the DGW sends the event report message tothe CGW, the DGW may add the service capability information of the DGWto one or more of event report messages, or may add, for example, afield to the event report message to indicate the service capabilityinformation of the DGW. For example, the field may be an IP allocationcapability.

Optionally, the IP allocation capability may be used to indicate an APN,an external server associated with the APN, or local address poolinformation of the DGW, or may include other indication information thatmay indicate that the DGW has the IP address allocation capability.

In a second manner, the service capability information of the DGW ispreconfigured in the CGW.

For example, the service capability information of the DGW may beconfigured in the CGW in an operation, administration and maintenance(OAM) manner.

Optionally, for example, the service capability information configuredin the CGW includes the following.

(1) Service information supported by the DGW and IP address allocationinformation indicating whether the DGW supports the service informationare configured in the CGW. In this case, the CGW may determine, based onthe service information requested by the terminal device and the locallystored service capability information of the DGW, whether the DGW has aservice capability to allocate the IP address for the serviceinformation requested by the terminal device. To be more specific, theCGW may search for the locally stored service capability information ofthe DGW, in order to determine whether there is a DGW to allocate the IPaddress for the service information requested by the terminal device.

(2) Service information or a service area identifier corresponding to anenterprise network is configured in the CGW (for example, it isstipulated that the DGW allocates an IP address for an enterprisenetwork service). In this case, the CGW may determine, based on theservice information requested by the terminal device, whether a serviceinitiated by the terminal device is an enterprise network service, orthe CGW may determine, based on location information (such as a cellidentifier (Cell ID) or a base station identifier (e.g., an eNodeB (eNB)ID)) of the terminal device, whether a dedicated enterprise network isaccessed by the terminal device (to be more specific, the CGW determineswhether a cell on which the terminal device camps is a serving cell ofthe enterprise network, or determines whether a base station connectedto the terminal device is a base station serving a particular enterprisenetwork), and determine, based on the foregoing determining result,whether to instruct the DGW to allocate the IP address for the terminaldevice. For example, if the terminal device accesses the dedicatedenterprise network, it is determined that the DGW is instructed toallocate the IP address for the terminal device. If it is determinedthat the terminal device does not access the enterprise dedicatednetwork, it is determined that the CGW allocates the IP address for theterminal device. In other words, the DGW is not instructed to allocatethe IP address for the terminal device, and so on.

Optionally, the service information requested by the terminal device mayinclude an access point name (APN) requested by the terminal device, andthe APN may be used to indicate a service type, and may further includeother service-related information requested by the terminal device. Theservice capability information of the DGW may include capabilityinformation indicating that the DGW allocates an IP address to the APN,for example, may indicate a particular APN to which the DGW is capableof allocating an IP address, and may further include otherservice-related capability information of the DGW.

The following uses some examples to describe a process of allocating theIP address by the DGW.

Example 1

Refer to FIG. 5.

1. In an attachment procedure of a terminal device or a PDN connectionprocedure requested by the terminal device, the terminal device sends anattachment request or a PDN connection establishment request message toan access network device (such as a base station), and the accessnetwork device sends the attachment request or the PDN connectionestablishment request message to an MIME. The MME may performauthentication on the terminal device. If the authentication succeeds,the MME may initiate a session establishment procedure to a core networkdevice. For example, the MIME may send a session establishment requestmessage to a CGW (in FIG. 5, an arrow is used to indicate that the CGWreceives the session establishment request message in the process, anddevices such as the access network device and the MIME are not shown),and the session establishment request message may carry an APN, aprotocol configuration option (PCO), location information of theterminal device, and the like. The APN carried in the sessionestablishment request message may be used to indicate a service typerequested by the terminal device. The PCO may include an allocationmanner of an IP address requested by the terminal device, in otherwords, may include address allocation manner information indicating thatthe IP address is allocated to the terminal device. The locationinformation of the terminal device may include any one or combination ofthe following: an identifier of a cell on which the terminal devicecamps, a tracking area identity (TAI), and an identifier of the basestation accessed by the terminal device. For example, the identifier ofthe cell on which the terminal device camps may include an E-UTRAN cellglobal identifier (ECGI), and the identifier of the base stationaccessed by the terminal device may include an eNB ID of the basestation accessed by the terminal device.

This embodiment of the present disclosure focuses on IP addressallocation. Therefore, for numerous parameter information included inthe PCO, this embodiment of the present disclosure focuses only on theaddress allocation manner information, and other parameter informationincluded in the PCO is not repeated. For example, the address allocationmanner information may be implemented using Address AllocationPreference included in the PCO. Address Allocation Preference maygenerally include two values, which respectively are IP addressallocation via non-access stratum (NAS) signaling and IP version 4(IPv4) address allocation via DHCPv4. If a value of Address AllocationPreference is IP address allocation via non-access stratum signaling, itindicates that when the terminal device is attached to a network, anetwork device allocates the IP address for the terminal device in aprocess of establishing a default bearer for the terminal device. If avalue of Address Allocation Preference is IPv4 address allocation viaDHCPv4, it indicates that a network device allocates the IP address tothe terminal device after establishing a default bearer for the terminaldevice.

2. The CGW determines, based on the APN carried in the sessionestablishment request message and locally stored service capabilityinformation of a DGW, whether the DGW has a capability to allocate an IPto the APN requested by the terminal device, in other words, whether theDGW is capable of allocating the IP address for the terminal device.

One CGW may be connected to a plurality of DGWs. In this case, afterreceiving a session establishment request, the CGW needs to select oneDGW for the terminal device, to provide a service for the terminaldevice. When selecting the DGW, the CGW needs to determine whether theselected DGW has a capability to allocate an IP to the APN requested bythe terminal device. When selecting the DGW, the CGW may consider aplurality of factors, for example, may use the location information ofthe terminal as a consideration factor, and may further consider any oneor combination of the following: the service type requested by theterminal device, current load of the DGW, a capability of the DGW (forexample, including whether the DGW supports a deep packet inspectioncapability), and similar information, and may further consider otherinformation. This is not limited in this embodiment of the presentdisclosure.

3. If it is determined that the DGW has a capability to allocate an IPto the APN requested by the terminal device, the CGW determines that theDGW allocates the IP address for the terminal device, and then the CGWsends an address allocation indication to the DGW.

Optionally, the address allocation indication may include the addressallocation manner information, and the address allocation mannerinformation may be used to indicate a manner in which the DGW allocatesthe IP address for the terminal device. The address allocation mannerinformation is obtained by the CGW from the session establishmentrequest message sent by the terminal device.

Optionally, the address allocation indication may further includeindication information, and the indication information may be used toinstruct the DGW to allocate the IP address for the terminal device.

In this embodiment of the present disclosure, a manner of the addressallocation indication is not limited, provided that the DGW maydetermine, using the address allocation indication, whether the IPaddress is allocated by the DGW to the terminal device. For example, theaddress allocation indication may be implemented using some existingmessages, for example, may be implemented using an Sx interface message,and the DGW may determine, using an existing information element in theaddress allocation indication, whether the IP address is allocated bythe DGW to the terminal device, or the DGW may determine, using anewly-added information element in the address allocation indication,whether the IP address is allocated by the DGW to the terminal device.For example, in this embodiment of the present disclosure, aninformation element specially configured to indicate whether the DGWallocates the IP address for the terminal device may be newly added tothe address allocation indication, and so on. To better understand thesolutions in the embodiments of the present disclosure, the followinguses two examples to describe different implementations of the addressallocation indication.

In a first implementation, if the CGW determines that the IP address isallocated by the DGW to the terminal device, the CGW sends the addressallocation indication for the terminal device to the DGW. Optionally,the address allocation indication may carry service informationrequested by the terminal device (for example, including the APN).Optionally, the address allocation indication may further carry theaddress allocation manner information (for example, including the PCO).Optionally, the address allocation indication may further carry theindication information, for example, the indication information isrepresented as an IP address allocation indication (IP allocationindication). The indication information may be used to instruct the DGWto allocate the IP address for the terminal device. For example, theaddress allocation indication may be implemented using an Sx interfacerequest message, or may certainly be implemented using another possiblemessage.

If the first implementation is used, in this case, if the CGW determinesthat the IP address cannot be allocated by the DGW to the terminaldevice, for example, the DGW may not have the capability to allocate theIP address to the APN requested by the terminal device, the CGW may sendthe APN to the DGW instead of sending the PCO and the indicationinformation. In other words, the address allocation indication does notcarry the address allocation manner information and the indicationinformation.

After the DGW receives the address allocation indication sent by theCGW, if the address allocation indication carries the APN, the PCO, andthe indication information, the DGW knows, by identifying the APN andthe indication information that are carried in the address allocationindication, that the IP address is allocated by the DGW to the terminaldevice, and then allocates the IP address for the terminal device in amanner indicated by Address Allocation Preference in the PCO. However,if the address allocation indication does not carry the PCO and theindication information, the DGW knows that the IP address is notallocated by the DGW to the terminal device, and the DGW does notallocate the IP address for the terminal device, in order to avoid an IPaddress conflict.

This is an explicit indication manner. In this indication manner, theDGW can relatively quickly determine whether the IP address is allocatedby the DGW to the terminal device, such that the indication mannerbrings a relatively good effect.

In a second implementation, if the CGW determines that the IP address isallocated by the DGW to the terminal device, the CGW may send theaddress allocation indication to the DGW. Optionally, the addressallocation indication may carry the service information requested by theterminal device (for example, including the APN). Optionally, theaddress allocation indication may further carry the address allocationmanner information (for example, including the PCO). For example, theaddress allocation indication may be implemented using the Sx interfacerequest message, or may be implemented using the other possible message.

If the second implementation is used, in this case, if the CGWdetermines that the IP address cannot be allocated by the DGW to theterminal device, for example, the DGW may not have the capability toallocate the IP address to the APN requested by the terminal device, theCGW may send the APN to the DGW instead of sending the PCO. In otherwords, the address allocation indication does not carry the addressallocation manner information.

After the DGW receives the address allocation indication sent by theCGW, if the address allocation indication carries the APN and the PCO,the DGW knows, by identifying the APN in the address allocationindication, that the IP address is allocated by the DGW to the terminaldevice, and then allocates the IP address for the terminal device in amanner indicated by Address Allocation Preference in the PCO. However,if the address allocation indication does not carry the PCO, the DGWknows that the IP address is not allocated by the DGW to the terminaldevice, and the DGW does not allocate the IP address for the terminaldevice, in order to avoid the IP address conflict.

Certainly, in addition to the two manners, the CGW may further addanother possible message to the address allocation indication, toinstruct the DGW, and this is not limited in this embodiment of thepresent disclosure.

The Sx interface request message described in step 3 may be the sessionestablishment request message of an Sx interface, or may be a bearerestablishment request message of the Sx interface, or may be anotherpossible request message such as a session management request message.

4. The DGW receives the address allocation indication of the CGW. If theIP address is allocated by the DGW to the terminal device, the DGWallocates the IP address for the terminal device in a manner indicatedby Address Allocation Preference in the PCO.

If the value of Address Allocation Preference is IP address allocationvia NAS signaling, to be more specific, this is used to instruct the DGWto allocate the IP address for the terminal device in the process ofestablishing the default bearer, the DGW may allocate the IP address forthe terminal device and need to add the allocated IP address for an Sxinterface request response message when sending the Sx interface requestresponse message to the CGW (this is used as an example in the example1). If the value of Address Allocation Preference is IPv4 addressallocation via DHCPv4, to be more specific, this is used to instruct theDGW to allocate the IP address for the terminal device after the defaultbearer is established, the DGW temporarily does not allocate the IPaddress for the terminal device. After the default bearer isestablished, the terminal device sends a request message to the DGW. TheDGW may then allocate the IP address for the terminal device aftersubsequently receiving the request message.

When allocating the IP address for the terminal device, the DGW may senda request to an HSS and obtain the allocated IP address from the HSS.Alternatively, the DGW may allocate the IP address for the terminaldevice based on a local address pool, to be more specific, may selectone IP address from the local address pool as the IP address allocatedto the terminal device. Alternatively, the DGW may allocate the IPaddress for the terminal device using an external mechanism. Theexternal mechanism may be that the DGW sends a request to an externalserver and requests the external server to allocate an IP address forthe terminal device. After allocating the IP address for the terminaldevice, the external server sends the allocated IP address for the DGW.In this way, the DGW completes a process of allocating the IP addressfor the terminal device using the external mechanism.

Optionally, the DGW may allocate the IP address for the terminal deviceusing different external mechanisms, for example, a Dynamic HostConfiguration Protocol (DHCP) mechanism may be used to allocate the IPaddress for the terminal device, or a Remote Authentication Dial In UserService (RADIUS) mechanism may be used to allocate the IP address forthe terminal device, or a Layer 2 Tunneling Protocol (L2TP) mechanismmay be used to allocate the IP address for the terminal device.

Optionally, if the DGW allocates the IP address for the terminal deviceusing the DHCP mechanism, the DGW may send an address allocation requestmessage to a DHCP server (generally, an address of the DHCP server maybe configured in the DGW). The address allocation request message isused to request the DHCP server to allocate an IP address for theterminal device. After receiving the address allocation request message,the DHCP server may allocate the IP address for the terminal device, andthe DHCP server may send the allocated IP address for the DGW.

Optionally, if the DGW allocates the IP address for the terminal deviceusing the RADIUS mechanism, the DGW may send an address allocationrequest message to an Authentication, Authorization and Accounting (AAA)server (generally, an address of the AAA server may be configured in theDGW). The address allocation request message is used to request the AAAserver to allocate an IP address for the terminal device. Afterreceiving the address allocation request message, the AAA server mayallocate the IP address for the terminal device, and the AAA server maysend the allocated IP address for the DGW.

Optionally, if the DGW allocates the IP address for the terminal deviceusing the L2TP mechanism, and the terminal device accesses the networkin a Point to Point Protocol (PPP) manner, the DGW may establish an L2TPlink to an LNS based on an address of an L2TP network server (LNS)(generally, the address of the LNS may be configured in the DGW). Afterthe LNS allocates an IP address for the terminal device, the DGW mayobtain the IP address using the established L2TP link.

In addition, in addition to allocating the IP address for the terminaldevice, the DGW may further perform a conventional bearer establishmentprocedure, for example, install a bearer context delivered by the CGW.

If the CGW does not instruct the DGW to allocate the IP address, the CGWmay allocate the IP address for the terminal device. In this case, theDGW does not allocate the IP address for the terminal device, andperforms only the conventional bearer establishment procedure, forexample, installs the bearer context delivered by the CGW.

5. The DGW sends an Sx interface request response message to the CGW. Ifthe IP address is allocated by the DGW to the terminal device, and avalue of Address Allocation Preference is IP address allocation via NASsignaling, the DGW adds, to the Sx interface request response message,the IP address allocated to the terminal device. If the IP address isallocated by the DGW to the terminal device, and a value of AddressAllocation Preference is IPv4 address allocation via DHCPv4, the DGWadds, to the Sx interface request response message, a field used tocarry the IP address (for example, may add a field used to indicate thatthe IP address is 0:0:0:0). If the CGW is responsible for allocating theIP address, in other words, the CGW does not instruct the DGW toallocate the IP address for the terminal device, to be more specific,the CGW does not send the address allocation indication to the DGW, theSx interface request response message does not carry the IP address ofthe terminal device.

After receiving the IP address that is allocated to the terminal deviceand that is sent by the DGW, the CGW may send the IP address for theMME, and the MME sends the IP address for the terminal device using theaccess network device.

Example 2

Referring to FIG. 6, a case in which an IP address is allocated by a DGWto a terminal device, and a value of Address Allocation Preference isIPv4 address allocation via DHCPv4 is described in detail.

For step 1 to step 5 of the example 2, refer to the example 1, and thefollowing describes steps different from the example 1.

6. After a default bearer is established, a DGW receives a requestmessage that is sent by a terminal device using a user plane connection(the terminal device is also not shown in FIG. 6, and the requestmessage is represented only by an arrow).

If the value of Address Allocation Preference is IPv4 address allocationvia DHCPv4, the DGW temporarily does not allocate the IP address for theterminal device, and an Sx request message that is sent by the DGW tothe CGW carries a field used to carry the IP address. In this case, theterminal device needs to send a request message again to request the IPaddress (for example, the request message may be a DHCP request message,or may be another possible request message). The request message maycarry service information requested by the terminal device, for example,may carry an APN requested by the terminal device, and the terminaldevice may directly send the request message to the DGW using the userplane connection (a link shown by a dashed line arrow in FIG. 6),without using a device such as the CGW.

7. The DGW allocates an IP address for the terminal device based onservice information carried in the request message.

Optionally, the DGW may allocate the IP address for the terminal deviceusing an external mechanism.

The DGW allocates the IP address for the terminal device using theexternal mechanism. Similar to the description in step 4 in the example1, different external mechanisms such as a DHCP mechanism, a RADIUSmechanism, or an L2TP mechanism may also be used to allocate the IPaddress for the terminal device. After receiving the request message,the DGW may determine, by resolving the service information carried inthe request message, which manner is used to allocate the IP address forthe terminal device.

Optionally, if it is determined that the IP address is allocated to theterminal device using the DHCP mechanism, the DGW may determine that aserver that allocates the IP address for the terminal device is a DHCPserver. An address of the DHCP server may be preconfigured in the DGW,and the DGW may send an address allocation request message to the DHCPserver based on the address of the DHCP server, in order to request theDHCP server to allocate an IP address for the terminal device. Afterreceiving the address allocation request message, the DHCP server mayallocate the IP address for the terminal device, and send the allocatedIP address for the DGW.

Optionally, if it is determined that the IP address is allocated to theterminal device using the RADIUS mechanism, the DGW may determine that aserver that allocates the IP address for the terminal device is an AAAserver. An address of the AAA server may be preconfigured in the DGW,and the DGW may send an address allocation request message to the AAAserver based on the address of the AAA server, in order to request theAAA server to allocate an IP address for the terminal device. Afterreceiving the address allocation request message, the AAA server mayallocate the IP address for the terminal device, and send the allocatedIP address for the DGW.

Optionally, if it is determined that the IP address is allocated to theterminal device using the L2TP mechanism, the DGW may determine that aserver that allocates the IP address for the terminal device is an LNS.An address of the LNS may be preconfigured in the DGW, and the DGW mayestablish a link to the LNS based on the address of the LNS, and send anaddress allocation request message to the LNS server using theestablished link, in order to request the LNS to allocate an IP addressfor the terminal device. After receiving the address allocation requestmessage, the LNS may allocate the IP address for the terminal device,and send the allocated IP address for the DGW using the establishedlink.

8. The DGW sends the allocated IP address for the terminal device usingthe user plane connection.

To be more specific, in this allocation manner, the DGW may directlysend the allocated IP address for the terminal device using the userplane connection, without using a device such as the CGW.

In this embodiment of the present disclosure, an execution body forallocating the IP address in different network scenarios may bedetermined, to be more specific, negotiation may be performed betweenthe CGW and the DGW to determine which of the two devices allocates theIP address for the terminal device, in order to avoid an IP addressconflict. In addition, the CGW may also undertake partial work ofallocating the IP address, in order to reduce a burden of the DGW. Inaddition, if the IP address is allocated using a local address pool, andin this case, if one CGW is connected to a plurality of DGWs, arelatively large quantity of IP addresses may need to be configured inthe local address pool of the CGW, such that an allocation requirementof the CGW can be met. This imposes a relatively high requirement on theCGW. If the DGW undertakes partial work of IP address allocation,pressure of the CGW can be reduced, and operation and maintenance costsof the CGW can be reduced.

Devices provided in the embodiments of the present disclosure aredescribed below with reference to the accompanying drawings.

Referring to FIG. 7A, based on a same concept of the disclosure, a firstcontrol plane network device is provided, and the control plane networkdevice may include a receiver 701 and a processor 702.

The processor 702 may include a central processing unit (CPU) or anapplication-specific integrated circuit (ASIC), or may include one ormore integrated circuits configured to control program execution, or mayinclude a hardware circuit developed using a field programmable gatearray (FPGA), or may include a baseband chip.

The receiver 701 may be configured to perform network communication withan external device.

Optionally, referring to FIG. 7B, the control plane network device mayfurther include a transmitter 703.

The transmitter 703 may be configured to perform network communicationwith an external device.

The transmitter 703 and the receiver 701 may be a same physical module,for example, may be a physical module that can implement receiving andtransmitting functions. For example, the physical module may be referredto as a transceiver. Alternatively, the transmitter 703 and the receiver701 may be separate physical modules.

The transmitter 703 and the receiver 701 may be connected to theprocessor 702 using a bus (this is used as an example in FIG. 7A andFIG. 7B), or may be separately connected to the processor 702 using adedicated connection cable.

Code corresponding to the methods described above is embedded into achip by designing and programming the processor 702, such that the chipcan perform the methods shown in FIG. 3 to FIG. 6 during running. How todesign and program the processor 702 is a technology well known to aperson skilled in the art, and details are not described herein.

The control plane network device may be configured to perform themethods described in FIG. 3 to FIG. 6, for example, may be the foregoingcontrol plane network device, which may be, for example, the foregoingCGW or the foregoing PGW-C. Therefore, for functions and the likeimplemented by the units in the control plane network device, refer tothe description of the foregoing methods. Details are not describedagain.

Referring to FIG. 8A, based on a same concept of the disclosure, anembodiment of the present disclosure provides a first user plane networkdevice, and the user plane network device may include a first receiver801 and a processor 802.

The processor 802 may include a CPU or an ASIC, may include one or moreintegrated circuits configured to control program execution, or mayinclude a hardware circuit developed using an FPGA, or may include abaseband chip.

The first receiver 801 may be configured to perform networkcommunication with an external device.

Optionally, referring to FIG. 8B, the user plane network device mayfurther include a first transmitter 803, and the first transmitter 803may be configured to perform network communication with an externaldevice.

Optionally, referring to FIG. 8C, the user plane network device mayfurther include a second receiver 804 and a second transmitter 805, andthe second receiver 804 and the second transmitter 805 may be configuredto perform network communication with an external device.

Optionally, referring to FIG. 8D, the user plane network device mayfurther include a third receiver 806 and a third transmitter 807, andthe third receiver 806 and the third transmitter 807 may be configuredto perform network communication with an external device.

The transmitters and the receivers may be connected to the processor 802using a bus (this is used as an example in FIG. 8A to FIG. 8D), or maybe separately connected to the processor 802 using a dedicatedconnection cable.

Code corresponding to the methods described above is embedded into achip by designing and programming the processor 802, such that the chipcan perform the methods shown in FIG. 3 to FIG. 6 during running. How todesign and program the processor 802 is a technology well known to aperson skilled in the art, and details are not described herein.

The user plane network device may be configured to perform the methodsdescribed in FIG. 3 to FIG. 6, for example, may be the foregoing userplane network device, which may be, for example, the foregoing DGW orthe foregoing PGW-U. Therefore, for functions and the like implementedby the units in the user plane network device, refer to the descriptionof the foregoing methods. Details are not described again.

Referring to FIG. 9, based on a same concept of the disclosure, anembodiment of the present disclosure provides a second control planenetwork device, and the control plane network device may include areceiving module 901 and a processing module 902. Optionally, thecontrol plane network device may further include a sending module 903.

In actual application, a physical device corresponding to the sendingmodule 903 may be the transmitter 703 in FIG. 7B, a physical devicecorresponding to the processing module 902 may be the processor 702 inFIG. 7A and FIG. 7B, and a physical device corresponding to thereceiving module 901 may be the receiver 701 in FIG. 7A and FIG. 7B.

The control plane network device may be configured to perform themethods described in FIG. 3 to FIG. 6, for example, may be the foregoingcontrol plane network device, which may be, for example, the foregoingCGW or the foregoing PGW-C. Therefore, for functions and the likeimplemented by the units in the control plane network device, refer tothe description of the foregoing methods. Details are not describedagain.

Referring to FIG. 10, based on a same concept of the disclosure, anembodiment of the present disclosure provides a second user planenetwork device, and the user plane network device may include areceiving module 1001 and a processing module 1002. Optionally, the userplane network device may further include a sending module 1003.

In actual application, the receiving module 1001 may communicate with aplurality of external devices. For example, a physical devicecorresponding to the receiving module 1001 may include any one orcombination of the following: the first receiver 801 in FIG. 8A to FIG.8D, the second receiver 804 in FIG. 8C and FIG. 8D, and the thirdreceiver 806 in FIG. 8D. A physical device corresponding to theprocessing module 1002 may be the processor 802 in FIG. 8A to FIG. 8D. Aphysical device corresponding to the sending module 1003 may include anyone or combination of the following: the first transmitter 803 in FIG.8B to FIG. 8D, the second transmitter 805 in FIG. 8C and FIG. 8D, andthe third transmitter 807 in FIG. 8D.

The user plane network device may be configured to perform the methodsdescribed in FIG. 3 to FIG. 6, for example, may be the foregoing userplane network device, which may be, for example, the foregoing DGW orthe foregoing PGW-U. Therefore, for functions and the like implementedby the units in the user plane network device, refer to the descriptionof the foregoing methods. Details are not described again.

It should be noted that, in FIG. 7A to FIG. 8D, a position of eachfunctional module is merely an example, and does not represent an actualposition of each functional module in a real device.

When receiving a session establishment request message, the controlplane network device may determine whether a first user plane networkdevice is capable of allocating an IP address for a terminal device. Ifthe first user plane network device is capable of allocating the IPaddress for the terminal device, the control plane network device mayinstruct the first user plane network device to allocate the IP addressfor the terminal device. In this way, which device allocates the IPaddress may be determined, and a case in which two devices allocate anIP address for one terminal device at the same time is avoided, therebyavoiding an IP address conflict.

In the present disclosure, it should be understood that the discloseddevice and method may be implemented in other manners. For example, thedescribed apparatus embodiment is merely an example. For example, theunit division is merely logical function division and may be otherdivision in actual implementation. For example, a plurality of units orcomponents may be combined or integrated into another system, or somefeatures may be ignored or not performed. In addition, the displayed ordiscussed mutual couplings or direct couplings or communicationconnections may be implemented through some interfaces. The indirectcouplings or communication connections between the apparatuses or unitsmay be implemented in electronic or other forms.

The units described as separate parts may or may not be physicallyseparate, and parts displayed as units may or may not be physical units,may be located in one position, or may be distributed on a plurality ofnetwork units. Some or all of the units may be selected according toactual needs to achieve the embodiments of the present disclosure.

Functional units in the embodiments of the present disclosure may beintegrated into one processing unit, or each of the units may be anindependent physical module.

When the integrated unit is implemented in the form of a softwarefunctional unit and sold or used as an independent product, theintegrated unit may be stored in a computer-readable storage medium.Based on such an understanding, all or some of the technical solutionsof the present disclosure may be implemented in a form of a softwareproduct. The computer software product is stored in a storage medium andincludes several instructions for instructing a computer device (whichmay be a personal computer, a server, or a network device) or aprocessor to perform all or some of the steps of the methods describedin the embodiments of the present disclosure. The foregoing storagemedium includes: any medium that can store program code, such as auniversal serial bus (USB) flash drive, a removable hard disk, aread-only memory (ROM), a random-access memory (RAM), a magnetic disk,or an optical disc.

The foregoing embodiments are merely used to describe the technicalsolutions of the present disclosure. The foregoing embodiments aremerely intended to help understand the methods in the embodiments of thepresent disclosure, and shall not be construed as a limitation on theembodiments of the present disclosure. Any variation or replacementreadily figured out by a person skilled in the art shall fall within theprotection scope of the embodiments of the present disclosure.

What is claimed is:
 1. An Internet Protocol (IP) address allocationmethod, comprising: sending, by a user plane network device, servicecapability information of the user plane network device to a controlplane network device; receiving, by the user plane network device, anaddress allocation indication from the control plane network device;allocating, by the user plane network device, an IP address for aterminal device based on the address allocation indication; and sending,by the user plane network device, the IP address to the control planenetwork device.
 2. The IP address allocation method according to claim1, wherein the address allocation indication comprises serviceinformation, and wherein allocating the IP address comprises allocatingthe IP address for the terminal device further based on the serviceinformation.
 3. The IP address allocation method according to claim 2,wherein the service information indicates a service type requested bythe terminal device.
 4. The IP address allocation method according toclaim 1, wherein the address allocation indication further comprisesindication information, and wherein the indication information indicatesto the user plane network device to allocate the IP address for theterminal device.
 5. The IP address allocation method according to claim1, wherein the address allocation indication comprises addressallocation manner information, and wherein the address allocation mannerinformation indicates a manner of allocating the IP address for theterminal device.
 6. A user plane network device, comprising: a receiverconfigured to receive an address allocation indication from a controlplane network device, wherein the address allocation indicationcomprises address allocation manner information, and wherein the addressallocation manner information indicates a manner of allocating anInternet Protocol (IP) address for a terminal device; a processorconfigured to allocate the IP address for the terminal device based onthe address allocation indication; and a transmitter configured to: sendservice capability information of the user plane network device to thecontrol plane network device, wherein the user plane network device iscapable of allocating the IP address for the terminal device; and sendthe IP address to the control plane network device.
 7. The user planenetwork device according to claim 6, wherein the address allocationindication comprises service information, and wherein the processor isconfigured to allocate the IP address for the terminal device furtherbased on the service information.
 8. The user plane network deviceaccording to claim 7, wherein the service information indicates aservice type requested by the terminal device.
 9. The user plane networkdevice according to claim 6, wherein the address allocation indicationfurther comprises indication information, and wherein the indicationinformation indicates to the user plane network device to allocate theIP address for the terminal device.
 10. The user plane network deviceaccording to claim 6, wherein the address allocation indication furthercomprises address allocation manner information, and wherein the addressallocation manner information indicates a manner of allocating the IPaddress for the terminal device.
 11. An Internet Protocol (IP) addressallocation method, comprising: receiving, by a control plane networkdevice, a request message, wherein the request message requestsestablishing a session for a terminal device, wherein the requestmessage comprises service information, and wherein the serviceinformation indicates a service type requested by the terminal device;determining, by the control plane network device based on the serviceinformation and service capability information of a user plane networkdevice, whether the user plane network device is capable of allocatingan IP address for the terminal device; sending, by the control planenetwork device, an address allocation indication to the user planenetwork device in response to determining that the user plane networkdevice is capable of allocating the IP address for the terminal device;receiving, by the user plane network device, the address allocationindication from the control plane network device; allocating, by theuser plane network device, the IP address for the terminal device basedon the address allocation indication; and sending, by the user planenetwork device, the IP address to the control plane network device. 12.The IP address allocation method according to claim 11, furthercomprising receiving, by the control plane network device, the servicecapability information of the user plane network device from the userplane network device.
 13. The IP address allocation method according toclaim 11, wherein the address allocation indication comprises addressallocation manner information, and wherein the address allocation mannerinformation indicates a manner in which the user plane network device isto allocate the IP address for the terminal device.
 14. The IP addressallocation method according to claim 13, further comprising obtaining,by the control plane network device, the address allocation mannerinformation using the service information in the request message. 15.The IP address allocation method according to claim 11, wherein theaddress allocation indication further comprises the service information,and wherein allocating the IP address comprises allocating the IPaddress for the terminal device based on the service information.
 16. Acommunications system for Internet Protocol (IP) address allocation,comprising: a user plane network device; and a control plane networkdevice configured to: receive a request message, wherein the requestmessage requests to establish a session for a terminal device, whereinthe request message comprises service information, and wherein theservice information indicates a service type requested by the terminaldevice; determine, based on the service information and servicecapability information of the user plane network device, whether theuser plane network device is capable of allocating an IP address for theterminal device; and send an address allocation indication to the userplane network device in response to determining that the user planenetwork device is capable of allocating the IP address for the terminaldevice, wherein the user plane network device is configured to: receivethe address allocation indication from the control plane network device;allocate the IP address for the terminal device based on the addressallocation indication; and send the IP address to the control planenetwork device.
 17. The communications system according to claim 16,wherein the control plane network device is further configured toreceive the service capability information from the user plane networkdevice.
 18. The communications system according to claim 16, wherein theaddress allocation indication comprises address allocation mannerinformation, and wherein the address allocation manner informationindicates a manner in which the user plane network device is to allocatethe IP address for the terminal device.
 19. The communications systemaccording to claim 18, wherein the control plane network device isconfigured to obtain the address allocation manner information using theservice information in the request message.
 20. The communicationssystem according to claim 16, wherein the address allocation indicationfurther comprises the service information, and wherein the user planenetwork device is configured to allocate the IP address for the terminaldevice based on the service information.